Biometric authentication indicates a technology to identify individuals by using biometric information such as fingerprint patterns or vein patterns. Fingerprint patterns on the surfaces of one's fingers or palms vary among individuals, and hence individuals may be identified by using these patterns. Veins of the palm or the like may be imaged by using near infrared radiation. The vein patterns vary among individuals so that individuals may be identified by the vein patterns.
Biometric authentication includes different types of authentication, namely, 1:1 authentication and 1:N authentication. The 1:1 authentication includes inputting an ID of each individual, and matching new biometric information and the registered biometric information of the individual. The 1:N authentication includes matching new biometric information and all the data of registered biometric information without inputting IDs or the like of the individuals. The 1:N authentication is convenient because IDs of individuals need not be input. However, the 1:N authentication may increase a rate of erroneously identifying a wrong person as the matched individual (a false acceptance rate, hereinafter called “FAR”) along with an increase in the number of N because new biometric information is matched with all the data of the registered biometric information. It is preferable that the accuracy in large-scale 1:N authentication be high.
In performing biometric authentication of individuals based on biometric information, matching a position of a living body at registration and its position at authentication relative to a sensor capturing biometric information may increase the matching accuracy as well as improving the accuracy of authentication. For example, there is a technology known in the art to guide a position of a living body at authentication by displaying an image of the living body captured at registration as a guide image. Further, there are technologies known in the art to guide a position of a hand of a person to be authenticated without delaying authentication operations regardless of the right hand and the left hand being held over a sensor (e.g., Patent Documents 1 and 2 described below).
However, in such related art technologies, the position of one of the left hand and the right relative to the sensor is matched at registration and at authentication as biometric information. Further, one of the left hand and the right hand captured as an image of the hand at registration is displayed as a guide image to guide the position of the hand at authentication.
Even though the positions of the living body at registration and at authentication are matched, it may be difficult to increase the matching accuracy to improve the accuracy of the authentication. Hence, there seems to be a limit to the reduction of FAR. To implement ten million accurate biometric authentications as well as introducing the biometric authentication into public services or the like of the government, FAR needs to be reduced even further.
To reduce FAR, matching the biometric information of the left and right hands may be considered. In this case, when matching the left and right hands is conducted using the same sensor, angles of the left and right hands held over the sensor are different unless the person to be authenticated is moved. When the biometric information of the left and right hands is registered at the same angles relative to the body of the person to be authenticated, the authentication is conducted without interruption when the person places or holds one of the hands at an angle similar to the angle at registration. However, the authentication may be interrupted when the person places or holds the other one of the hands at the angle differing from the angle at registration.